[en] In JT-60 machine, usage of fluorocarbon as an alternate coolant to a cooling channel of toroidal field coil (TF coil) in which a crack was detected is investigated. Fluorinert (a registered trademark of 3M) liquid which is one of fluorocarbon was reviewed, and liquid 'FC-43' was found as an appropriate one for TF coils cooling because of its physical properties about boiling point and thermal capacity. Fortunately, Fluorinert does not have impact on the greenhouse effect for the earth under the temperature of its boiling point. And thermal analysis shows that the cooling effectiveness obtained with liquid 'FC-43' for TF coils is rather well. Moreover, corrosion tests were carried out between liquid 'FC-43' and materials used in JT-60 by considering deterioration of TF coils. The test results demonstrate that there is no problem in applying liquid 'FC-43' as a coolant to cooling channel of TF coils. Results obtained above conclude that usage of fluorocarbon is one of the effective means to perform further experiments in JT-60. (author)